Novak Djokovic of Serbia eyes the ball during his men's semi-final match against Ernests Gulbis of Latvia at the French Open tennis tournament at the Roland Garros stadium in Paris June 6, 2014.(STEPHANE MAHE/REUTERS)

Serbia's Novak Djokovic serves the ball during the semi-final match of the French Open tennis tournament against Latvia's Ernests Gulbis at the Roland Garros stadium, in Paris, France, Friday, June 6, 2014.(Michel Spingler/AP)

Ernests Gulbis of Latvia serves to Novak Djokovic of Serbia during their men's semi-final match at the French Open tennis tournament at the Roland Garros stadium in Paris June 6, 2014.(GONZALO FUENTES/REUTERS)

Novak Djokovic of Serbia serves to Ernests Gulbis of Latvia during their men's semi-final match at the French Open tennis tournament at the Roland Garros stadium in Paris June 6, 2014.(GONZALO FUENTES/REUTERS)

Referee Carlos Ramos of Portugal, right, watches Latvia's Ernests Gulbis, left, return the ball during the semi-final match of the French Open tennis tournament against Serbia's Novak Djokovic at the Roland Garros stadium, in Paris, France, Friday, June 6, 2014.(Michel Spingler/AP)

Ernests Gulbis of Latvia returns the ball to Novak Djokovic of Serbia during their men's semi-final match at the French Open tennis tournament at the Roland Garros stadium in Paris June 6, 2014.(GONZALO FUENTES/REUTERS)

Novak Djokovic of Serbia casts his shadow as he serves to Ernests Gulbis of Latvia during their men's semi-final match at the French Open tennis tournament at the Roland Garros stadium in Paris June 6, 2014.(JEAN-PAUL PELISSIER/REUTERS)

Novak Djokovic of Serbia returns the ball to Ernests Gulbis of Latvia during their men's semi-final match at the French Open tennis tournament at the Roland Garros stadium in Paris June 6, 2014. Picture taken with zoom-out effect.(STEPHANE MAHE/REUTERS)

Latvia's Ernests Gulbis returns the ball during the semi-final match of the French Open tennis tournament against Serbia's Novak Djokovic at the Roland Garros stadium, in Paris, France, Friday, June 6, 2014.(Darko Vojinovic/AP)

Serbia's Novak Djokovic picks up his racket after throwing it on the court during the semi-final match of the French Open tennis tournament against Latvia's Ernests Gulbis at the Roland Garros stadium, in Paris, France, Friday, June 6, 2014.(Darko Vojinovic/AP)

Ernests Gulbis of Latvia covers his head with a towel during his men's semi-final match against Novak Djokovic of Serbia at the French Open tennis tournament at the Roland Garros stadium in Paris June 6, 2014.(VINCENT KESSLER/REUTERS)

Latvia's Ernests Gulbis returns the ball during the semi-final match of the French Open tennis tournament against Serbia's Novak Djokovic at the Roland Garros stadium, in Paris, France, Friday, June 6, 2014.(David Vincent/AP)

Latvia's Ernests Gulbis returns the ball during the semi-final match of the French Open tennis tournament against Serbia's Novak Djokovic at the Roland Garros stadium, in Paris, France, Friday, June 6, 2014.(David Vincent/AP)

Latvia's Ernests Gulbis returns the ball during the semi-final match of the French Open tennis tournament against Serbia's Novak Djokovic at the Roland Garros stadium, in Paris, France, Friday, June 6, 2014.(David Vincent/AP)

A view shows glass windows reflecting spectators and Philippe Chatrier Court during the men's semi-final match between Novak Djokovic of Serbia and Ernests Gulbis of Latvia at the French Open tennis tournament at the Roland Garros stadium in Paris June 6, 2014.(STEPHANE MAHE/REUTERS)

Serbia's Novak Djokovic screams before smashing his racket during the semi-final match of the French Open tennis tournament against Serbia's Novak Djokovic at the Roland Garros stadium, in Paris, France, Friday, June 6, 2014.(Michel Euler/AP)

Novak Djokovic of Serbia reacts during his men's semi-final match against Ernests Gulbis of Latvia at the French Open tennis tournament at the Roland Garros stadium in Paris June 6, 2014.(JEAN-PAUL PELISSIER/REUTERS)

Yui Kamiji of Japan serves to Aniek van Koot of the Netherlands during their wheelchair tennis women's final match at the French Open Tennis tournament at the Roland Garros stadium in Paris June 6, 2014.(GONZALO FUENTES/REUTERS)

Shingo Kunieda of Japan returns the ball to Stephane Houdet of France during their wheelchair tennis men's final match against at the French Open Tennis tournament at the Roland Garros stadium in Paris June 6, 2014.(STEPHANE MAHE/REUTERS)

Serbia's Novak Djokovic picks up the racket he smashed on the court during the semi-final match of the French Open tennis tournament against Latvia's Ernests Gulbis at the Roland Garros stadium, in Paris, France, Friday, June 6, 2014.(Darko Vojinovic/AP)

Britain's Andy Murray returns the ball to Spain's Rafael Nadal during their semi-final match of the French Open tennis tournament at the Roland Garros stadium, in Paris, France, Friday, June 6, 2014.(Michel Euler/AP)

Rafael Nadal of Spain returns the ball to Andy Murray of Britain during their men's semi-final match at the French Open tennis tournament at the Roland Garros stadium in Paris June 6, 2014.(JEAN-PAUL PELISSIER/REUTERS)

Britain's Andy Murray returns the ball to Spain's Rafael Nadal during their semi-final match of the French Open tennis tournament at the Roland Garros stadium, in Paris, France, Friday, June 6, 2014.(Michel Spingler/AP)

Spain's Rafael Nadal returns the ball to Britain's Andy Murray during their semi-final match of the French Open tennis tournament at the Roland Garros stadium, in Paris, France, Friday, June 6, 2014.(Michel Spingler/AP)

Rafael Nadal of Spain returns the ball to Andy Murray of Britain during their men's semi-final match at the French Open tennis tournament at the Roland Garros stadium in Paris June 6, 2014.(JEAN-PAUL PELISSIER/REUTERS)

Britain's Andy Murray walks back to his chair for a break as he plays Spain's Rafael Nadal during their semi-final match of the French Open tennis tournament at the Roland Garros stadium, in Paris, France, Friday, June 6, 2014.(David Vincent/AP)

Rafael Nadal of Spain celebrates after winning his men's semi-final match against Andy Murray of Britain at the French Open tennis tournament at the Roland Garros stadium in Paris June 6, 2014.(JEAN-PAUL PELISSIER/REUTERS)

A general view shows the Philippe Chatrier court during the men's semi-final match between Andy Murray of Britain and Rafael Nadal of Spain at the French Open tennis tournament at the Roland Garros stadium in Paris June 6, 2014.(STEPHANE MAHE/REUTERS)